The invention relates to a screw press for separation of liquid from solid liquid mixtures, especially pulp suspensions, with a casing with perforations for liquid and a screw shaft provided in it between which a circular gap is formed through which the solid liquid mixture is pressed and with a counter pressure device in the area of the discharge end of the circular gap.
The counter pressure device is used to create at the end of the circular gap a backup of the solid liquid mixture with the liquid largely extracted so as to further increase the pressure in the circular gap to extract even more liquid from the solid liquid mixture. In the area of the counter pressure device or subsequent to it the solid liquid mixture with the liquid largely extracted has to be redirected so it can be discharged.
In the state of the art, e.g. AT 398 090 B the redirection is achieved radially outwards whereby the casing surrounding the discharge area is relatively large, however essentially larger than the casing of the screw, as it is necessary to not only have space for the counter pressure device, but also for the solid liquid mixture with the liquid largely extracted. This is not only a disadvantage due to the increased space requirement but also in view of the design, as the relatively large discharge casing has a worse stiffness which has to be compensated by a reinforced construction.